Production of low cold-test oils by



G. D. KERNS Nov. 3, 1959 PRODUCTION OF LOW COLD-TEST OILS BY UREA DEWAXING Filed March 8, 1957 United States Patent Cfliice Patented Nov. 3, `1959,

PRODUCTION F LOW COLD-TEST OILS Bi(l l UREA DEWAXING j l' Gordon D. Kems, Hammond, Ind;',;assignor to Standard `Oil Company; Chicago, Il l., a corporation-,ofjndlana .Appui-Lamu March s, 1957, seria1N0.6 44,761,

s Claims. (cl. 20s-2s) l pour points. Although these proposed methodsfor dewaxing petroleum stocks by means of. ureay are suitable vfor small-scale operations, their. use ona commercial scale presents operating; -diiiculties and disadvantages which render them unattractive. Thus, for example, it has beenv proposed to carry out the dewaxing operation batchwise in a reaction vessel equipped with a filter the bottom thereof, by means of which the dewaxed oil is separated from thesolid adduct; in addition to fore.

going the operating efficiencies and advantages attending the use of a continuous process, such a methodfwhen applied commercially requires unreasonably long ltration times because of the thicklter lcakewhichis produced. Otherproposedmetliods contact the waxy oil with solutions of urea; thus two liquid phases are present in thereactor, giving rise to operatingdiiculties occasioned bythe formation of emulsions which areA often dicult to break. Still other methods which contemplate the Vuse kof solid urea involve costly and dicult methods of operation such as the use of screw conveyors for transporting solid materials. y

An object of the present invention is to provide'limproved methods, and means. for the dewaxing of petroleumj stocks. Another object is to provide an improved continuous vprocess for the production of low cold-test -oils onan industrial scale with minimum investment and operatingcosts while avoiding hitherto encountered operational difficulties. this invention will be apparent lto those skilled in the art' from the following description.' e

OtherVA objects and advantages -of f In accordance with the method ofthtis invention, low cold-test oils having pour points within the rangeof about 10 to 70 F. are produced vby contacting a wax-containingy hydrocarbon oil havinga viscosity {within the range of about 40 to 300 SSU at 100 F. arid pour point of about 0` to 100 F. with finely dividedsolid urea in an amount of about 3 to 8, and preferably lfrom about 4- to 6,V pounds per pound of wax in theoil, about ,0.5% tov about 10% by volume, based on thewaxy oil, of methanol, and about 0.1 toabout 3 volumesl of an inert hydrocarbon diluent liquid, at least a portion of which is used as a slurrying agent for regenerated and recycled solid urea. The contacting is continued at a temperature of about 40 to about 120 F., and preferably from about to. 1,0091 F., -for a time suficientto effect ad- 2 duct formation, normally about 0.1}to 1.5 hours,'after which the adduct andV any unreacted urea isvsep'arated from the diluent oil by means of filtration, centrifugation, or the like. The filtrate, consisting of -diluent and dewaxed oil containing a portion of the methanol supplied to the contacting step, is stripped of methanol and diluent, which are recovered for reuse, yielding the desired low cold-test product. The adduct cake is repulped to form a slurry withl recycled wax-containing diluent liquid from al subsequent washing zone, and the sltlrry is heated to, a temperature above, aboutl 180 F. but below the melting point of urea and ispumped to a de-l composing zone.' 1n the decomposing zone `the adduct decomposes, liberating solid particles of regenerated urea and the adducted wax which goes into solution in the diluent liquid.` ``fl`he methanol present flashesoff as a vapor and isy condensed and recovered, for reuse. The particles of regenerated solid urea settle to the bottom of the decomposing zone, leaving a supernatant solution of liberated wax in diluent liquid, which is removed continuously and stripped to recover the diluent for reuse. The regenerated solid urea is collected at the bottom of the decomposingzone and is'pumped as a slurry to the irst of [two washing zones where recycled diluentl is added as a wash liquid. The solid urea is separated from the,l wash liquid by continuous decantation and is pumped asa slurry to the second washing zone where the wash- 'ing operation is repeated. yFrom the second washing 1 zone urea slurry is rrecycled to contact freshcharging stock. The wash liquid is used to slurry t11e`adduct` cake, as vdescribed above. v The rprocess of my invention provides an improved method whereby oils having extremely low pour points can be' prepared. These products are useful as transformer oils, automatic transmission fluids, refrigerator oils and the like, which have heretofore been prepared from certain low-Wax crudes, such as Kittrell Vand Winkler. Owing tothe decreasing supply of Alow-wax crudes, however, it has become necessary to `devise another technique for producing low cold-test oilsfwhich can vbe'u'sed onan industrial scale. This .,isfsnupplied by the method of my invention, which is a unitary ycontinuous process providing the utmost in simplicity of operatiom'minimum investment cost, andmost efficient utilization of kal1 process materials, leadingfto minimumoperating cost.

In producing the desired low cold-test oils there is used as the charging stock a petroleum kfraction having a viscosity of about 40 to 300 SSU at 100 F.. and a pour pointwithinthe range from yabout 0 F. to about 100 F., suitably a Mid-Continent fraction. These viscosities correspond in general to the SAE 10, SAE 5, and lighter y grades. The minimum pour point attainable appears to depend on the viscosity of the oil, Varying directly as a logarithmic function thereof. Previous solvent dewaxing, in some cases, alsoA affects the'pour point obtained by urea-dewaxing according to my,technique. Oils having viscosities of,v 40 to 150 ,SSU at 100"v F. are urea-devvaxed to the same low pour point whether previously v dewaxed or not..- In the viscosity range of V-200 SSU,

urea-dewaxing produces oils of` low pour point only from oils vwhich havefbeen previously 'dewaxed by .conventional meansv toV a pour pointv Vof. l, about 0 tol 10 F. From' 200 to 300 SSU, kurea formsadducts with the waxes inboth undewaxed distillates, and cold-pressedroils, but

theirnprovernents in pour .pointj are notas great as in thecase of lowerviscosity oils.k In all cases,however, `it

is preferred that-the charging stock be previously de- Waxed to a pour point of about 0 F. to 10 F. by any convenient means suchas propane dewaxing, cold-pressing,V or thelike. This Iisdesirable in order to minimize of adductablewaxy rmaterials in the charging stock, it isv necessary that at least about3 pounds of urea per pound of adductable material in the charging stock besupplied. In practice this may range from about 3 to 8 pounds of urea per poundof wax, and preferably from about 4 to 6. Thepresence `of solid materials in such quantities and the fact the urea-wax adducts tend to be stickyy and pasty in nature makes it desirable that thecharging stock be diluted with a hydrocarbondiluent which is a further v'quantity of' Ithe liquid used to form the slurry of urea.` The diluent, which is advantageously employed in proportions up to 300% or more based on the charging stock,'thins the mixture, insuring better contact between lthe ureaiand oil, andfa'cilities separation of solid materials from'dewaxed oil, asV by filtration.

The quantity of diluent to be'uscd will depend on the viscosity'o'f the charging stock, the wax content thereof, and the efficiency of the mixingV and separating equipment. It is', of course, desirable to use diluents in as low a concentation as possible in order tov minimize the'difiiculty and expense of recovery thereof. I prefer to use be- 60 F. are less satisfactory because of contacting and filtering difficulties arising from increased viscosity of the reaction mixture. Since the adduction reaction is exothermic, it will be found convenient to cool the mixture entering the reactor to a temperature about 5-10 F. below the maximum temperature desired in the reactor.

In this way the liberated heat of reaction is absorbed by f the reactants, and'no external cooling means need be used. Otherwise, some` means for controlling thefmaximum temperature in the reactor must be provided.

From the reactor the slurry of adduct, unreacted urea, dewaxedV oil and methanol isf conveyed to a separation zone for removal of thesolid materials from Lthe diluted dewaxed oil. The separation zone is preferably a conventional drum-type filter, although other means such as a centrifuge can` be used. When a drum filter is used, it is advantageous to carry on the filtration with an inert gas such as nitrogen under superatmospheric pressure within the case of the filter. The use of inert gas pressure' at this point has an important advantage in addition to increasing the speed of filtration.v The inert gas which leaves the filter along with lthe filtrate is subsequently-recovered,l recompressed, and recycled to the filter case. In this way it soon becomes saturated with tween about 50,'and 150% by volume thereof, based' on the charging stock. The diluent may be any v.hydrocarbon liquid which'is unreactive with urea underthe conditions lemployed and which'has apboiling point sutiiciently removed' from that of the 'product oil to permitv a cle'an separation therefrom by distillation. Among the e diluents which can be used, although not necessarily with equivalent results, are naphthas and other hydrocarbons,

lincluding pentane, isopentane, isooctane, benzene, toluene, light alkylate, and the like. A particularly suitable diluent is alight alkylate obtained by alkylation ofa -f mixed butylene stream with isobutane land subsequent fractionation to. remove high boiling material. Light allrylate` is: inert to 'urea at all temperatures and has a boiling range of about 120 to 350 F., permitting it tobe 'readilystripped from? the dewaxed oil, lleaving a treated material free from extraneous substances;

To the mixturefjof diluted oil andl solid urea, there is added an ,activator which is required for adduct formation within `a reasonabletime. Suitable activators include oxygcnated solvents rfor-urea, such as water and the lower alcohols, among vwhichmethanol'is particularly preferredLfWhen methanol isl used, it is added in an amount of -about0.5%"fto about 10%, and preferably about 3%, by volume based on the waxy oil, a quantity which in the absence of any other liquid is sufficient merely to moisten the surface ofthe urea particles without the appearance of any'subst'antial liquid phase. In somecasesit may be desirable to use a iminor amount-of water in conjunction with the methanol. Y"In such cases between about 2 fand" 10% `by volumeV based on the i5 methanol may' Abefadded. l -v The mixture of charging stock, diluent, urea and activator is transferred to a reactor wherein adduction be'- tween urea and the waxy materials in the'oil takes place.

The reactor is suitably a vertically-'elongated vessel con- 5? taining one or'morel doughnut bafiies which serves to divide they reactor into two or more mixing stages, each of which is` supplied with means for stirring -the reaction inixtu're. e The reactor should be sized such that the average residence ltime within the vessel Vis withinthe range betweenfabout 30,-'1 'and '125 hours or more, and preferablyv about one hour. VAdduction occurs-atany temperature'beloww about 130 F., with the range'from ab`ou't60" tti-100- F. being preferred. Temperatures above about '100 F. are' less satisfactory` because of increasing instability-of the'adduct,- and temperatures below about within the-pores of theV filter cloth. -By inhibiting Vthe evaporation offmethanol, blinding of the filter'cloth with urea particles isA discouraged. l Thefltrate, consistingof low-pour'oil, diluent, and a portion -ofthe methanol activator, is Vseut'to a vessel wherein the inert gas is separated, recompressed, and recycled to the filter. The diluted oil is then stripped of methanol and diluent, which are recovered and recycled. The stripped product thereby 'obtained is thedesired low cold-test oil. Y

The adduct cake from the filter is washed with recycled diluent liquid to remove occluded oil and is then reslurried with a recycled stream of diluent which has been used to wash'the regenerated urea in a subsequent zone to be 5 more fully described below. Sufficient diluent liquid is supplied toform a slurry which is easily pumped by conventional slurry pumps, suitably having a solids content within the range from about 20 to 60 weight percent, and preferably about 30%. The slurry is heated to a tem'- perature withinthe range above about 180 F. but below the melting point of urea and preferably between about 200 and 240 Rand is'passed to a vessel wherein vapors of methanol and a portion of the diluent flash overhead, are condensed, separated and recycled. When the adduct decomposes, theiliberated wax goes into solution in the diluent liquid and the urea is regenerated as finely divided particles which `settleto the` bottomof thedecomposer, where they are collected as a slurry containing about 20 to '75% solids, and preferably about 60%, which is pumped to the Vfirst of twofwashing stages wherein the regenerated ureais washed of occludedfwax andoil..y A vsolid-.free solution of liberated wax in diluent liquidi is withdrawn from a point near the ,top of the decomposer and is iiashed and stripped to separate diluent fwhich isl recycled andwax which may be further processed as'desired, lor used asa charging stock to. a` catalytic'cra'cking operation.' r

*e The slurry'of regenerated urea leaving the decomposer contains' significant quantities of waxdissolved in the diluentliquidformingv the slurry. t The slurry is washed toV remove these materials'by a process of continuous decantation, i.e., by continuously addingwash liquidfal-y lowing the solid particles to settle, and removing a solidfree streamvof wash liquid.` As vwash liquid there is'added to the slurry -recycled diluent, suitably in a proportion from about to about 150% by volume, and preferably transferred to a vessel wherein the urea particles continu-` ously settle to the bottom and the wash liquid isy taken oi overhead. The particles of urea are collected at the bottom of the washer andy pumped as a slurry to a'second similar stage wherein thewashing operation isl repeated. A portion of the wash liquid leaving the firstwasher (e.g., about `60-70722) is combined with'the vwax-'rich solution leaving the decomposer and is vfurther processed together with the'latter stream. '1 he remaining wash' liquid from the lirst washer yis combined with the similar stream from the second washer and the combined stream i`s .`used t0 slurry the adduct cake from the lter. From' the'bottom ofthe second washer a slurry of regenerated and washed urea particles in diluent liquid is transferred toV a pulp storage tank, wherein make-up quantities of diluent and ureaare added asneeded, and is then recycled to contact fresh charging stock. v c

lMy` invention will be more fully understood from the fdllowing detailedtdescription thereof in conjunction with the accompanyinggure, which isa schematic ow dia-` gram of a commercial plant Aforvthe production of low coldltetst oils.v Althoughzrnydnvention'is applicable to the production of low cold-test oils having pour'points ranging from about .10 F; to -70 F. from charging stocks having viscosities in the range from about 40 to 300 SSU at 100 F. and pour points within the range from about 0 to 100 F., it 'will be described with particularreference to ureaftlewaxing 'of a 'distillate having' aviscosity of about 80 vSSU at 100 F., a pour p ointf about 0k F., andan adductable wax content of about 7% by. weight.k The charging stock 11in an amount of about `'1030 barrels perday, is combined with a slurry of recycled urea 12 inli'ght alkylate (boiling range 120- 350 E), said slurry comprising about- 60 weightA percentsolidurea, in an amount of about v586 barrels per day and is passed through line 13 tol cooler 14 wherein thetemperatureis lowered to about 80v F. To the combined oil and urea mixture thereis addedrecycled diluent 15 comprising light alkylate in an amount of/about 690 barrels per day (including approximately 2.7 barrels of make-up diluent), recycled methanol 16 in an amount of about 39 barrels per day- (including about 1.2 barrels of make-up methanol), and water 17 as needed in an amount up to 10 volume percent based o n the `methanol. The

'combinedfmixture lispassed through line`18to reactor 19,v

whichcomprises' a cylindrical vessel about 8` feet in diam- .eter Iand 12 feet high, equipped with two doughnut baffles (e.g., 20) which divide the reactor into three mixving stages each equipped with a stirrer (e.g., 21). The heat'of reaction liberated'within the reactor causes the v'temperature of the mixture to riseto a maximum of about 90 F. The size of reactor 19 issuch that the average residence time of the Vmixture thereinis about one hour. With other feed stocks the liow rates may be adjustedso 'that an adduction time Vbetween about 0.1 and-1.5 hours Ior more is used.

From the reactor 19 the reaction'products flow through line 22 to filter 23, which is a conventional continuous Yrotary Adrum filter with an effective area of about 150 square feet operated lin an atmosphere of nitrogen under vpressure supplied through liner24. The pressure of nitrogenmay rangesuitably from 30 to 50 p.s.i.g."or higher as desired. Within the iilter the rotating drum 25 forms ahlter cake from the slurry 26 in which it is partially immersed., Thisflter cakelis dislodged from the rotating drum :by gas-pressure and is directed bydoctor blade V27 into the repulper 28. Prior to being dislodged the filter Vcake isy washed on the 'filter drum to remove occluded oil -with a stream of recycled `light alkylatel29 entering :throughline 30, in anarnount of about690 barrels per day, and partially dried witha stream of nitrogen. With- {mgthe repulper28 the adductcake vis reslurried-'with re- -Cycledlight alkylate entering throughfline31 by' means 6. of stirrer 32, forming a slurrycomprising about 16190? barrels per day having a solids content of about weight percent.

The reslurried adduct is transferred through line 33 I by-rneans of slurry pump 34 and is heated by heater 3SY to a temperature of about220 F. invorder to decompose- Othertemperatures rangingup toabout 240 the adduct. F. and ydown to Aabout 200V or belowv may also be used, althoughbelow 200 F. regeneration of urea becomes increasingly incomplete. Regeneration temperatures above about 240 F. are less desirable because excessive temperatures that exist locally in heater 35 tend l diluent.

to. approachthe melting point of yurea and'cause the decompositionpof an increasingly large portion of the urea passed through heater 35. The heated a'dductstreamV is conveyed into decomposer 36 maintained at a'pressure of about 20 p.s.i.g. and a temperature -of about 220 This combination of pressure and temperature'permits essentially all of the methanol contained withinthe entering stream to liash oft together with a portion of the Removal of the methanol at this point prevents the readduction of the wax present in the diluent liquid with the urea as the temperature is lowered in subsequent stages of the operation. Obviously, other temperatures and pressures can be used in the decomposer, provided that the temperature is sufficiently high t0 insure complete regeneration-blut not high enough to-melt lo'r decompose the urea,' and thatthe pressure at Vthe given temperature is low enough to permit substantially complete removalv of the'methanolwithoutashing olf excessive quantities of diluent. The vaporsr 'of methanol and diluent pass e through line 37 to condenser 56, where they are condensed and passed to separator 57 in which4 diluent'iis separated from methanol and each is recycled for reuse, the diluent through line 58 and the methanol throughy line 59.A

Within the decomposer 36 the liberated Wax goes into solution in the diluent liquid and the urea is regenerated in theform of linely divided particles. An essentially solid-free solution-of wax in diluent (about 1090 barrels per day) is taken oit at a point near the top of decomf poser 36 through line 38, while the particles of regenerated'urea settle to the cone-shaped hopper 36a at the bottom of the decomposer 36 where they are collected and are pumped as a slurry containing about weight percent solidsV bymeans of slurry pump 40 through lines 39 and 41 to washer 42. Also added, to washer v42 is washV liquid consisting of recycledy lightalkylate supplied through line 43'in an amount Vof` about 710 'barrelsrpe'r day. In washer 42 the urea particles again settleto'the bottom and are conveyed as aslurry (about 60weight percent solids) through line 44 to the second washer ,45 to which is "also added an additional 710 barrels per day ofA wash liquid (light alkylate) through line 46. The wax-containing-wash liquid leaves washer 42 through line 47 in an amount of about 710 barrels per day and is split 1nto two streams, a portion (about 450 barrels per day) going through line 48 to join a similar wax-rich diluent 'pressed by compressor 63 c solution 'leaving the decomposer 36 through line 38. The

via line 55 to contact fresh charging stock.-

The filtrate leaving filter/2 3 throughv line 60, comprismg dewaxed oil, diluent, and a vportion f-themethanOl, passes to filtrate accumulator 61ffzwhere1the inert gas (nitrogen) is separated through line 62 and is recom;- for reuse. Make-up nitrogen is addedl through line 64 as needed. The diluted oil (about 2320 barrels per day.) leaves accumulator 61 via line65 andV pump 66, is heated by means of heater 67 to a temperature of about 200 F. and enters flash drum 68 wherein essentially all the methanol and a portion of the diluentflashv off,Y are passed through line 69 and condenser 56 into separator 57 where these materials are separated .and recycled. T he diluted oil, stripped of its methanol content, leaves the ash drum through line 7 0 and pump 71 into thestripper 72, which is operated at a pressure of about 3-10 p.s.i.g. and a temperature of about 230 F'. at the top and 380 F. at the bottom with open steam 73 being supplied at the bottom ,through line 74.Y I,Steam and diluent vapors leave stripper 72 through line 75 torcondenser 76 and separator 77 wherein the water is separated and discarded through line78 and a portion (about 520 barrels per day) of the condensed diluent is returned as reflux to stripper 72 through line 79`and valver80. The stripped low pour oil leaves the stripper through line 81 to a suitable dehydrator (optional, and not shown) and then to storage. The low cold-test product, amounting to about 910 barrels per day, has a pour point of about -45 F. Operating in a similar manner, the plant is capable of Aproducing about 750 barrels per day of --50Y F. pour oil from a charging stock having a viscosity of about 50 SSU,(100 F.) and an initial pour point of about F., andabout 1120 bar-I rels'per day of a V-25 F. pour oil from a charging stock having aviscosity of about 220 SSU (100 F.) and an initial pourrpointfoffabout 0 F.l t i Y Y The combined wax-rich diluent streams leaving decomposer 36 and washer 42,.. through lines 38 and 48 respectively passvia line 82 and pump ,83 to heater 84 wherein the stream is heated to about 350 F. and introducedto wax flash tower 85. Most of the diluent flashes offthrough line 86 and the remaining vconcentrated solution of wax in diluent leaves tower 85 through line 87 and pump 88 to heater 89, whereinrit is heated to about 400 F., and enters wax stripper `90 to which is supplied open steam through line 91. Steam and diluent vapors leave stripper 90 through line 92, are combined with diluent vapors in line 86 leaving wax flash tower 85, and are passed lthrough line 93Y and condenser 76l toseparator 77. A portion of the separated diluent isA returned as reux to wax flash tower 85 (about 390 barrels periday) through 'lines 94 and 95 and to Wax stripper 90 (about 5 barrels per day) through line 96. The remaining diluent leaves separator 77 through line 97 and is recycled to the 'contacting' stage. Stripped wax product (about 120 barrels per day) leaves wax stripper 90` through line 98 to storage.

While I have described in detail specific examples of my invention, it shouldbe understood that Vvarious alternative operating procedures and operating conditions will be apparent to those skilled in the art.

'I claim: i

1; A continuous process for dewaxing a wax-containing hydrocarbon oil having a viscosity in the range of about 40 to about 300 SSU at 100 F., which process comprises adding to said oil solid urea in an amount of at least about three pounds per pound ofzwax in the oil, about 0.5% to 'about 10% by. volume, based on the waxy oil, of methanol, and about 0.1 to about 3 volumes of an inert hydrocarbon ydiluent liquid per volume of said oil, contacting the resulting mixture at about 40 to about 120 F. for a timeV kto effect adduct formation, 'separating adduct and unreacted urea from diluted oil, Vseparating'methanol and diluent from the oil to obtain a product of low pour point, repulping the separated adduct and unreacted urea with'waX-containing diluent liquid from a subsequent washingv zone and pumping the repulped materialV to a decomposing zone which is at a temperaturejabove about 180 F. but below the melting point of ureafremoving methanol vapor from thev de'- `composing zone and condensing thevapor for reuse, sepavrating a solution ofzlibcrated wax in diluent liquid from 8.' regenerated solid urea, stripping the wax solution to remove diluent liquid therefrom, washing the regenerated solid urea with diluent liquid, recycling wax-containing wash liquid to said repulping step, slurrying the washed regenerated solidrurea with diluent liquid and recycling the resulting slurry to the contacting step, and returning to the contacting step methanol and diluent liquid sepa-V rated from the diluted oil, from the wax solution, and from the decomposing step.

2. A continuous process for treating a wax-containing Mid-Continent oil having a viscosity in the range of about 40 to aboutl 300 SSU at 100 F. and a pour point in the range of about 0 to about 100 F., and obtaining therefrom a low cold-test oil having a pour point in the range of about 10 F. to about -70 F., which process comprises adding to said oil solid finely-divided urea in an amount of about 4 to 6 pounds per pound of wax in the oil, about 0.5% to about 10% by volume, based on the waxy oil, of methanol, and about 0.5 to about 1.5 volumes pei volume of said oil of an inert hydrocarbon diluent comprising a liquid alkylate fraction boiling between about 120 F. and 350 F., contacting the resulting mixture at about F. to about 100 F. for about 0.1 to about 1.5 hours to effect adduct formation, separating adduct and unreacted urea from diluted oil, separating methanol and diluent from the oil to obtain the desired low cold-test product, repulping the separated adduct and unreacted urea with wax-containing liquid from a subsequent washing'zone to obtainra slurry and pumping the resulting slurry to a decomposing zone which is at a temperature between about 200 F. and about 240 F., removing methanol vapor from the decomposing zone and condensing the vapor for reuse, separating a solution of liberated wax in diluent liquid from regenerated solid urea, stripping the wax solution to remove diluent liquid therefrom, washing the regenerated solid urea with diluent liquid by continuous decantation, recycling Wax-containing wash liquid to said repulping step, slurrying the washed regenerated solid urea with diluent liquid and recycling the resulting slurry to the contacting step, and returning to the contacting step methanol and diluent liquid separated from the diluted oil, from the wax solution, and from the decomposing step.

3. A continuous process for dewaxing a wax-containing Mid-Continent oil having a viscosity in the range of about 40 to 300 SSU at 100 F. and a pour point of about 0 F. to about 10 F. and obtaining therefrom a low cold-test oil having a pour point of about 10 F. to about 70 F., which process comprises adding tosaid oil solid urea in an amount of about 4 pounds per pound of wax in the oil, about 3% by volume, basedon the waxy oil, of methanol, and about l volume per volume of said oil of an inert hydrocarbon diluent comprising a liquid alkylate fraction having a boiling range of about 120 F. to about 350 F., contacting the resulting mixture at about F. for about one hour to effect adduct formation, filtering adduct and unreacted urea from diluted oil, separating methanol and diluent from the oil to obtain the desired low cold-test product, repulping the separated adduct and unreacted urea with suicient wax-containing diluent liquid from a subsequent washing zone to obtain a slurry having a solids content of about 30 weight percent, pumping the repulped material to a decomposing zone which is at a temperature of about 220 F. 'anda pressure of about 20 p.s.i.g., flashing methanol-vapor from the decomposing zone and condensing the vapor .for reuse, allowing the heated repulped material to settle and separating therefrom a solid-free solution of-liberated waxY in diluent liquid and a slurry of regenerated solid urea having a solids content of about 60 weight percent, stripping the wax solution to remove diluent therefrom, washing the slurry by adding thereto a wash liquid comprising said diluent liquid in an amount of about 1.2 Volumes pervolume of slurry, stratifying and separating Said mixture to obtain solid-free wax-containing Wash liquid and a slurry of urea having a solids content of about 60 weight percent, repeating said washing operation, recycling wax-containing Wash liquid to said repulping step, recycling the slurry of washed regenerated solid urea to the contacting step and returning to the contacting step methanol and ydiluent liquid separated from the diluted oil, from the wax solution, and from the decomposing step.

References Cited in the le of this patent UNITED STATES PATENTS Adams et al. Mar. 11, 1952 Skelton et al. Dec. 1, 1953 Weitkamp etal Dec. 6, 1955 Thornes Ian. 17, 1956 Rumberger et a1 Feb. 11, 1958 

1. A CONTINUOUS PROCESS FOR DEWAXING A WAX-CONTAINING HYDROCARBON OIL HAVING A VISCOSITY IN THE RANGE OF ABOUT 40 TO ABOUT 300 SSU AT 100*F., WHICH PROCESS COMPRISES ADDING TO SAID OIL SOLID UREA IN AN AMOUNT OF AT LEAST ABOUT THREE POUNDS PER POUND OF WAX IN THE OIL, ABOUT 0.5% TO ABOUT 10% BY VOLUME, BASED ON THE WAXY OIL, OF METHANOL, AND ABOUT 0.1 TO ABOUT 3 VOLUMES OF AN INERT HYDROCARBON DILUENT LIQUID PER VOLUME OF SAID OIL, CONTACTING THE RESULTING MIXTURE AT ABOUT 40* TO ABOUT 120*F. FOR A TIME TO EFFECT ADDUCT FORMATION, SEPARATING ADDUCT AND UNREACTED UREA FROM DILUTED OIL, SEPARATING METHANOL AND DILUENT FROM THE OIL TO OBTAIN A PRODUCT OF LOW PUR POINT, REPULPING THE SEPARATED ADDUCT AND UNREACTED UREA WITH WAX-CONTAINING DILUENT LIQUID FROM A SUBSEQUENT WASHING ZONE AND PUMPING THE REPULPED MATERIAL TO A DECOMPOSING ZONE WHICH IS AT A TEMPERATURE ABOVE ABOUT 180*F. BUT BELOW THE MELTING POINT OF UREA, REMOVING METHANOL VAPOR FROM THE DECOMPOSING ZONE AND CONDENSING THE VAPOR FOR REUSE, SEPARATING A SOLUTION OF LIBERATED WAX DILUENT LIQUID FROM REGENERATED SOLID UREA, STRIPPING THE WAX SOLUTION TO REMOVE DILUENT LIQUID THEREFROM, WASHING THE REGENERATED SOLID UREA WITH DILUENT LIQUID, RECYCLING WAX-CONTAINING WASH LIQUID TO SAID REPULPING STEP, SLURRYING THE WASHED REGENERATED SOLID UREA WITH DILUENT LIQUID AND RECYCLING THE RESULTING SLURRY TO THE CONTACTING STEP, AND RETURNING TO THE CONTACTING STEP METHANOL AND DILUENT LIQUID SEPARATED FROM THE DILUTED OIL, FROM THE WAX SOLUTION, AND FROM THE DECOMPOSING STEP. 